The present disclosure is generally related to determining a glasses and/or a contacts prescription for a patient with a refractive error in need of correction. Many people have refractive errors of the eye which cause them to be either myopic (commonly known as nearsightedness) or hypermetropic (commonly known as farsightedness). One of ordinary skill in the art will understand that myopia refers to a refractive defect of the optical properties of an eye that causes images to focus forward of the retina (i.e. a refractive error). Those optical defects are typically caused by, among other things, defects of the cornea, elongation of the eye structure, other conditions, or a combination of those conditions. Hyperopia, on the other hand, refers a refractive error of the optical properties of an eye that causes images to focus behind the retina. Those optical defects are the result when the optics of the eye are not strong enough for the front to back length of the eye. Myopia and hyperopia have one component, a sphere measurement, which indicates the strength or power necessary to correct for the optical defects.
Astigmatism refers to a refractive error that causes light entering the eye to focus on two points rather than one. It is caused by an uneven power of the cornea. An astigmatism has two components, an axis measurement, which indicates the angle along which any image viewed by the patient is distorted, and a cylinder measurement, which indicates the strength or power of the distortion. Myopia, hyperopia, and astigmatism are the principle refractive errors that cause patients to seek treatment to correct their vision problems.
A manifest refraction analysis is a diagnostic tool used by ophthalmologists and optometrists whereby a patient's refractive error is tested to indicate whether the patient would benefit from correction with glasses or contact lenses. As part of that technique, a patient looks through a phoropter while the ophthalmologist or optometrist evaluates each of the patient's eyes. A retinal reflex diagnosis technique is often used to assess the magnitude of the refractive error present in the patient's eyes. Subjective feedback from the patient is used to refine the manifest refraction, which involves the patient making choices between image quality as different lenses having different powers are slid into place in the phoropter. These refractive errors can be corrected with lenses, typically spectacle lenses, known as glasses, or contact lenses, which are applied directly to the eye. They can also be corrected with various types of surgery. At the end of the manifest refraction analysis, the ophthalmologist or optometrist may produce a prescription for glasses, contact lenses, and/or refractive surgery.
Other methods for determining the refractive error of a patient include known diagnostic devices such wavefront sensors, refractometers, and others that are well known in the art. Some of these diagnostic devices use computers to assist in determining the refractive error of the patient. For example, one implementation of a wavefront-type refractor that is well known in the art uses a “Hartmann-Shack” sensor to measure the wavefront of a light beam generated from an illumination spot projected on the retina and passed through the eye's optics. In such a wavefront type refractor, a probe beam from a laser or a super-luminescent diode is projected onto the retina through the eye's optics. Light scattered by the retina passes through the eye's optics, and emerges through the eye's pupil. The wavefront of the emerging beam carries refractive information relating to the eye's optics. For example, if the eye is emmetropic (i.e., the eye's optics are without refractive error), the wavefront of the emerging beam should be flat. Relay optics relay the wavefront emerging from eye's pupil onto the Hartmann-Shack sensor. The Hartmann-Shack sensor measures the distortion of the wavefront and provides that information to a computer to compute the refractive errors of the eye due to aberrations of the eye's optics.
Each of the above-described techniques for determining a patient's refractive error requires the patient to travel to a place where such machines or doctors are present and available to perform the determination. And, having traveled to a doctor's office, a patient then has to pay for the time and services of the doctor, which may or may not be covered by their health insurance. This can be both expensive and inconvenient for a patient.
For a patient who desires contacts, a second charge generally applies for a “fitting.” This charge is frequently unnecessary because most contacts manufacturers only offer one or a few base curve and diameter combinations, meaning there is only one or a few possible “fits” for that contact. When a patient has worn contacts before and is comfortable in their previous brand, there is no need to perform a “fitting.” Despite this, it is commonly required by doctor's offices that a “fitting” be performed, and the accompanying fee charged. Health insurance seldom covers this fee. In some cases, the doctor may require that the patient make another, separate office visit to have their “fitting.” Therefore, determining a contacts prescription can be even more expensive and inconvenient for a patient.
In addition, the cost of the above described machinery (phoropter, wavefront refractor, etc.) is prohibitive to ownership by an individual not engaged in a medical practice, so patients do not have the option of determining their own glasses or contacts prescription outside of a medical practice setting.
Furthermore, in-office subjective astigmatism tests generally only determine a patient's axis prescription within 10° of accuracy.
Thus, there exists a need for a more convenient, less costly, more accurate way for patients to determine and receive glasses and contacts prescriptions.